A method for producing cadmium cake from cadmium-containing fumes

Abstract

The present application relates to a kind of method for producing cadmium cake from cadmium fume, belonging to the field of cadmium recovery.The present application treats cadmium fume by leaching, neutralization and precipitation, acid dissolution, oxidation and neutralization impurity removal, replacement and briquetting, wherein, by adding cadmium fume leaching solution to the reverse neutralization operation of alkali solution during neutralization, the amount of precipitate entering the cadmium hydroxide chloride is effectively reduced;after acid dissolution of cadmium hydroxide, the acid solution is oxidized to increase the valence of impurities such as arsenic and iron, and then alkaline material is added to precipitate high-valence impurities, achieving the removal of arsenic, iron and other impurities.The present application not only makes sponge cadmium easy to briquetting, but also reduces the escape concentration of AsH3 gas during zinc powder replacement of cadmium precipitation, improving the safety of operation.

Description

Technical Field

[0001] This invention belongs to the field of cadmium recovery technology, specifically, it relates to a method for producing cadmium cake from cadmium-containing dust. Background Technology

[0002] During crude lead smelting, over 90% of the cadmium in the furnace feed material is enriched in the flue dust. Other impurities such as fluorine and chlorine also accumulate in the flue dust. When the cadmium concentration in the flue dust reaches 15% or higher, the flue dust rate increases, increasing the load on the smelting furnace dust collection system, affecting the dust collection efficiency of the electrostatic precipitator, reducing the effective production load of the crude lead system, and thus impacting economic efficiency. Open-circuit treatment of lead flue dust can reduce its impact on the smelting process; the cadmium in the open-circuit flue dust usually needs to be recovered.

[0003] Patent CN116814960A discloses a process for treating cadmium-containing flue dust. The technical solution involves leaching cadmium from the flue dust, then adding an alkaline solution to the leachate to neutralize and precipitate the cadmium, producing cadmium hydroxide. Finally, the cadmium hydroxide is dissolved in acid and used to produce cadmium cake or cadmium yellow. The drawback is that the neutralized cadmium hydroxide has a high chloride content. During acid dissolution, chloride and cadmium enter the solution together, making it impossible to effectively remove chloride ions from the acid solution. Furthermore, the acid solution contains impurity ions such as Fe and As. When zinc powder is used to replace the cadmium in the acid solution, As... 3+ The generation of AsH3 gas will affect operational safety. Arsenic, chlorine and iron ions will affect the bonding performance of cadmium sponge, making it difficult or even impossible to press the cadmium sponge into cakes. Cadmium sponge is extremely easy to oxidize. If it cannot be pressed into cakes, it will not be able to enter the refined cadmium production line. Summary of the Invention

[0004] To overcome the problems existing in the background technology, the present invention provides a method for producing cadmium cake from cadmium-containing dust. By controlling the neutralization process, chlorine is prevented from precipitating with cadmium hydroxide, thereby reducing the chlorine content in cadmium hydroxide and making the cadmium hydroxide contain less chlorine. - When zinc powder is added to cadmium sponge after reducing the concentration to 0.04-0.08%, the emission of AsH3 gas is reduced, improving the working environment. Furthermore, through oxidation and neutralization, Fe and As impurities in the cadmium solution are removed, reducing the impact of arsenic, iron, and other impurity ions on the bonding performance of the cadmium sponge and improving the quality of the cadmium cake.

[0005] This invention is achieved through the following technical solution: The method for producing cadmium cake from cadmium-containing dust includes the following steps: (1) Leaching: The cadmium in the cadmium dust is leached by water leaching or acid leaching; liquid-solid separation is performed to obtain filtrate 1 and filter residue 1; (2) Neutralization and precipitation: reverse neutralization is used to precipitate cadmium in filtrate 1 and prevent the formation of basic cadmium chloride. After liquid-solid separation, filtrate 2 and cadmium hydroxide are obtained. (3) Acid dissolution: Add acid solution to dissolve cadmium hydroxide; (4) Oxidation and neutralization to remove impurities: The acid-soluble slurry is oxidized and neutralized to remove impurities, and the liquid and solid are separated to obtain filtrate 3 and filter residue 2; (5) Displacement and blistering: Add zinc powder to the filtrate 3 to displace cadmium sponge, and then blister the cadmium sponge to obtain cadmium cake.

[0006] Furthermore, the reverse neutralization described in step (2) involves adding the filtrate 1 from step (1) to the neutralizing agent.

[0007] Furthermore, the neutralizing agent is a sodium hydroxide solution or a sodium carbonate solution.

[0008] Furthermore, in step (2), the neutralization precipitation conditions are: room temperature, time 0.5-1.0h, and final pH value 10.5-11.0.

[0009] Furthermore, the acid dissolution conditions in step (3) are: temperature 50-70℃, time 1.0-2.0h, and final pH value 2.0-3.0.

[0010] Furthermore, the oxidation and neutralization removal in step (4) refers to first adding an oxidant to oxidize the low-valence ions that are harmful to cadmium replacement and agglomeration into high-valence ions, and then adding alkaline materials to neutralize the high-valence ions before adding them into the slag.

[0011] Furthermore, the oxidant used in step (4) is potassium permanganate; the alkaline material used is quicklime powder.

[0012] Further, in step (4), potassium permanganate of 0.4-0.8 g / L and quicklime powder of 1-2 g / L are added sequentially, at a temperature of 70-85℃ and a time of 0.5-1.0 h.

[0013] Furthermore, the acid solution in step (3) is one or both of dilute sulfuric acid and zinc electrolysis waste liquid.

[0014] Furthermore, filter residue 1 and filter residue 2 are sent to lead smelting. Beneficial effects

[0015] This invention effectively prevents the formation of basic cadmium chloride by employing reverse neutralization, thereby reducing the chlorine content entering cadmium hydroxide from 0.8-1.2% to 0.04-0.08%, making the subsequently produced sponge cadmium easier to agglomerate. Through acid dissolution followed by oxidation and neutralization to remove impurities, harmful impurities such as Fe and As are first oxidized to higher valence ions, and then these higher valence ions are neutralized and precipitated, effectively removing impurities such as iron and arsenic. This not only makes the sponge cadmium easier to agglomerate but also avoids the escape of AsH3 gas during zinc powder replacement precipitation, improving operational safety. The sponge cadmium produced by this invention is easy to agglomerate and has high purity, and can be directly sent to a refined cadmium production line. Attached Figure Description

[0016] Figure 1 This is a simplified process flow diagram of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are all within the scope of protection of this invention.

[0018] The method for producing cadmium cake from cadmium-containing dust includes the following steps: (1) Leaching Cadmium in the cadmium-containing flue dust was leached using conventional methods, namely water leaching or acid leaching. After liquid-solid separation of the leached slurry, filtrate 1 and filter residue 1 were obtained. Filter residue 1 was sent back to lead smelting 1.

[0019] (2) Reverse neutralization precipitation Conventional neutralization involves adding a neutralizing agent to filtrate 1, increasing the pH value of the slurry from low to high; the reverse neutralization described in this invention involves adding filtrate 1 to a neutralizing agent, decreasing the pH value of the slurry from high to low.

[0020] When cadmium-containing dust is leached in neutral or acidic conditions, the chlorine in the dust also enters the leachate along with the cadmium. During the neutralization and precipitation of cadmium in the leachate using conventional methods, i.e., adding a neutralizing agent to the leachate, the pH value of the slurry changes from low to high. In the pH range of 7.2-10.5, basic cadmium chloride (CdOHCl) precipitates and enters the cadmium hydroxide, resulting in cadmium hydroxide containing Cl. - High chloride content (0.8-1.2%) negatively impacts the subsequent utilization of cadmium hydroxide. This invention employs reverse neutralization, with the final pH controlled at 10.5-11.0. Because the pH of the neutralized slurry decreases from high to low, the formation range of basic cadmium chloride is avoided, thus reducing the chloride content of cadmium hydroxide. -Reduced to 0.04-0.08%.

[0021] Reverse neutralization precipitation technology conditions: temperature is room temperature, time is 0.5-1.0h, and the final pH value is 10.5-11.0. The neutralized slurry is separated into liquid and solid, and filtrate 2 and filter residue are obtained. Filtrate 2 is returned to step (1) to leach cadmium, and the filter residue is cadmium hydroxide, which is then entered into step (3).

[0022] The neutralizing agent used is a sodium hydroxide or sodium carbonate solution.

[0023] (3) Acid solubility Cadmium hydroxide is dissolved by adding an acid solution. The acid solution is one or both of dilute sulfuric acid and zinc electrolysis waste liquid. Acid dissolution technical conditions: temperature 50-70℃, time 1.0-2.0h, final pH value 2.0-3.0.

[0024] (4) Oxidation and neutralization to remove impurities In the filtrate 1 obtained in step (1), in addition to F and Cl, there are also harmful impurities such as Fe and As that affect subsequent displacement or flocculation. During the neutralization and precipitation in step (2), harmful impurities such as Fe and As will also enter cadmium hydroxide. During acid dissolution, the above-mentioned harmful impurities will dissolve along with cadmium and must be removed in order not to affect displacement or flocculation.

[0025] By adding an oxidizing agent, the impurities dissolved during acid dissolution are oxidized to higher valence ions. Then, an alkaline material is added to hydrolyze and precipitate these impurity ions into the slag. The oxidizing agent used is potassium permanganate, and the alkaline material is slaked lime powder.

[0026] Impurity removal technical conditions: Add potassium permanganate (0.4-0.8 g / L) and quicklime powder (1-2 g / L) sequentially. Add the quicklime powder immediately after the oxidant is added. Maintain a temperature of 70-85℃ for 0.5-1.0 h. Separate the slurry into liquid and solid phases to obtain filter residue 2 and filtrate 3. Filter residue 2 is returned to lead smelting.

[0027] (5) Displacement and compaction Zinc powder is added to filtrate 3 to displace the sponge cadmium. The sponge cadmium is then pressed into cadmium cake, which is then used in the production of refined cadmium. Zinc is recovered from the displaced liquid.

[0028] To illustrate the present invention more clearly, the following embodiments will be described in detail. Example 1

[0029] The cadmium-containing dust composition (%wt) used in this embodiment is: Pb 48.27, Cd 10.35, As 0.56, F 0.22, Cl 0.82.

[0030] Cadmium-containing fumes were added to zinc electrolytic waste liquid for acidic leaching. Liquid-solid separation yielded filtrate 1 and filter residue 1. The composition of filtrate 1 was: Cd 25.69 g / L, F 300 mg / L, Cl 200 mg / L, As 236 mg / L. Filter residue 1 was returned to lead smelting.

[0031] Filtrate 1 was added to a sodium hydroxide solution under the following conditions: room temperature, 0.5 h, and a final pH of 10.5. The neutralized slurry was then separated into solid and liquid components to obtain filtrate 2 and cadmium hydroxide. Filtrate 2 was returned to the cadmium-containing flue dust for acid leaching. The cadmium hydroxide composition (%wt) was: Cd 74.26, F 0.032, Cl 0.043.

[0032] Cadmium hydroxide was dissolved using dilute sulfuric acid. The acid dissolution conditions were: temperature 50℃, time 1.0 h, final pH 2.0. The composition of the solution after acid dissolution was: Cd 160.85 g / L, F 68 mg / L, Cl 96 mg / L, Fe 390 mg / L, As 140 mg / L. After acid dissolution, impurities were removed directly by oxidation without liquid-solid separation. The impurity removal conditions were: potassium permanganate 0.8 g / L and quicklime powder 2 g / L were added sequentially (quicklime powder was added after potassium permanganate, the same as in the following examples), temperature 70℃, time 1.0 h. The slurry was then separated into liquid and solid phases to obtain filter residue 2 and filtrate 3. Filter residue 2 was fed into lead smelting. The composition of filtrate 3 was: Cd 160.06 g / L, F 8.93 mg / L, Cl 98 mg / L, Fe 1.32 mg / L, As 0.16 mg / L.

[0033] Zinc powder was added to filtrate 3 to replace cadmium. During the replacement process, the concentration of arsine gas at the work site was 0.01 ppm, which met the occupational health requirements. The replaced cadmium sponge had good adhesion properties and could be pressed into cadmium cakes to enter the refined cadmium production line. Zinc was recovered from the replacement liquid.

[0034] Comparative Example 1

[0035] The cadmium-containing fume used was the same as in Example 1.

[0036] Cadmium-containing fumes were added to zinc electrolytic waste liquid for acidic leaching. Liquid-solid separation yielded filtrate 1 and filter residue 1. The composition of filtrate 1 was: Cd 25.69 g / L, F 300 mg / L, Cl 200 mg / L, As 236 mg / L. Filter residue 1 was returned to lead smelting.

[0037] Sodium hydroxide was added to filtrate 1, and cadmium precipitation was neutralized using conventional methods. The technical conditions were: room temperature, 0.5 h, and a final pH of 10.5. The neutralized slurry was then separated into liquid and solid components, yielding filtrate 2 and filter residue. Filtrate 2 was returned to the cadmium-containing flue gas for acid leaching, and the filter residue was cadmium hydroxide. The composition of cadmium hydroxide (%wt) was: Cd 73.91%, F 0.050%, Cl 1.12%, indicating that the prepared cadmium hydroxide had an extremely high Cl content.

[0038] Cadmium hydroxide was dissolved using dilute sulfuric acid. The technical conditions for acid dissolution were: temperature 50℃, time 1.0 h, and final pH value 2.0. The composition of the solution after acid dissolution (Cd g / L, other components mg / L) was: Cd 158.66, F 66, Cl 2450, Fe 386.42, As 132.

[0039] After acid dissolution, impurities are removed directly by oxidation without liquid-solid separation. The impurity removal conditions are as follows: potassium permanganate 0.8 g / L and quicklime powder 2 g / L are added sequentially (quicklime can be added after potassium permanganate, the same applies to the following examples), temperature 70℃, time 1.0 h, liquid-solid separation of the slurry, obtaining filter residue 2 and filtrate 3. The main components of filtrate 3 (Cd g / L, the rest mg / L) are: Cd 159.35, F 8.93, Cl 2 440, Fe 1.92, As 0.14.

[0040] Zinc powder was added to filtrate 3 to replace cadmium. During the replacement process, the concentration of arsine gas at the work site was 0.01 ppm, which met occupational health requirements. The replaced cadmium sponge had extremely poor bonding properties and could not be pressed into cadmium cakes.

[0041] Comparative Example 1 shows that the cadmium hydroxide obtained by neutralization and precipitation using conventional methods has an extremely high Cl content. Even after acid dissolution and impurity removal steps, the cadmium sponge obtained by displacement cannot be pressed into cadmium cakes and cannot be used in the refined cadmium production line. Example 2

[0042] The main components (%wt) of the cadmium-containing flue dust used in this embodiment are: Pb 33.27, Cd 30.35, As 1.86, F 0.42, Cl 1.08.

[0043] The cadmium-containing dust was leached in water, and after liquid-solid separation, filtrate 1 and filter residue 1 were obtained. The main components of filtrate 1 (Cd g / L, the rest mg / L) were: Cd 72.30, F 450, Cl 2500. Filter residue 1 was returned to lead smelting.

[0044] Filtrate 1 was added to a sodium carbonate solution under the following conditions: room temperature, 1.0 h, and final pH of 11.0. The neutralized slurry was then subjected to liquid-solid separation to obtain filtrate 2 and filter residue. Filtrate 2 was returned to the cadmium-containing flue gas for water leaching, and the filter residue was cadmium hydroxide. The main components of cadmium hydroxide (%) were: Cd 75.06, F 0.048, and Cl 0.052.

[0045] Cadmium hydroxide was acid-dissolved using zinc electrolysis waste liquid. The acid dissolution conditions were: temperature 70℃, time 2.0 h, final pH 3.0. The main components of the solution after acid dissolution (Cd g / L, other components mg / L) were: Cd 170.45, F 90.26, Cl 120.01, Fe 370, As 82. After acid dissolution, impurities were removed directly by oxidation without liquid-solid separation. The impurity removal conditions were: potassium permanganate 0.5 g / L and quicklime powder 1 g / L were added sequentially; the oxidation temperature was 85℃, and the time was 0.5 h. Liquid-solid separation was then performed to obtain filter residue 2 and filtrate 3. Filter residue 2 was sent to lead smelting. The main components of filtrate 3 (Cd g / L, other components mg / L) were: Cd 167.85, F 10.93, Cl 120.30, Fe 1.36, As 0.09.

[0046] Zinc powder was added to filtrate 3 to replace cadmium. During the replacement process, the concentration of arsine gas at the work site was 0.01 ppm, which met occupational health requirements. The replaced cadmium sponge had good adhesion properties and could be completely pressed into cadmium cakes for use in the refined cadmium production line. Zinc was recovered from the replacement solution.

[0047] Comparative Example 2

[0048] The acid-dissolved solution in Example 2 was directly separated into liquid and solid without oxidation to remove impurities. The filtrate was then replaced with zinc powder. During the replacement process, the amount of arsine gas generated on-site was 0.25-0.50 ppm, which did not meet occupational health requirements. The cadmium sponge produced by the replacement had extremely poor bonding properties and could not be pressed into cadmium cakes, thus it could not be used in the refined cadmium production line.

[0049] Comparative Example 2 shows that if cadmium hydroxide is dissolved in acid without being oxidized to remove impurities, the high content of impurities such as Fe and As will cause the arsine gas at the work site to exceed the standard, and the displaced cadmium sponge cannot be pressed into cakes.

[0050] Note: Unless otherwise specified, all percentage contents mentioned in this invention are mass percentage contents.

[0051] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for producing cadmium cake from cadmium-containing dust, characterized in that, Includes the following steps: (1) Leaching Cadmium in cadmium-containing dust is leached out by water immersion or acid immersion; liquid-solid separation is performed to obtain filtrate 1 and filter residue 1. (2) Neutralization and precipitation Reverse neutralization is used to precipitate cadmium in filtrate 1 and prevent the formation of basic cadmium chloride. After liquid-solid separation, filtrate 2 and cadmium hydroxide are obtained. The reverse neutralization is to add filtrate 1 from step (1) to a neutralizing agent. The pH value at the end of the reverse neutralization is 10.5-11.

0. (3) Acid solubility Add acid to dissolve cadmium hydroxide; (4) Oxidation and neutralization to remove impurities The acid-soluble slurry was oxidized and neutralized to remove impurities, and then the liquid and solid were separated to obtain filtrate 3 and filter residue 2. (5) Displacement and compaction Zinc powder was added to filtrate 3 to replace the cadmium sponge, and then the cadmium sponge was pressed into clumps to obtain cadmium cake.

2. The method according to claim 1, characterized in that, The neutralizing agent is a sodium hydroxide solution or a sodium carbonate solution.

3. The method for producing cadmium cake from cadmium-containing dust according to claim 1, characterized in that, In step (2), the neutralization precipitation conditions are: room temperature and time 0.5-1.0h.

4. The method for producing cadmium cake from cadmium-containing dust according to claim 1, characterized in that, The acid dissolution conditions for step (3) are: temperature 50-70℃, time 1.0-2.0h, and final pH value 2.0-3.

0.

5. The method for producing cadmium cake from cadmium-containing dust according to claim 1, characterized in that, The oxidation and neutralization removal mentioned in step (4) refers to first adding an oxidant to oxidize the low-valence ions that are harmful to cadmium replacement and agglomeration into high-valence ions, and then adding alkaline materials to neutralize the high-valence ions before adding them into the slag.

6. The method for producing cadmium cake from cadmium-containing dust according to claim 5, characterized in that, The oxidant in step (4) is potassium permanganate; the alkaline material is quicklime powder.

7. The method for producing cadmium cake from cadmium-containing dust according to claim 5 or 6, characterized in that, Step (4) add potassium permanganate 0.4-0.8 g / L and quicklime powder 1-2 g / L in sequence for oxidation, neutralization and impurity removal; the oxidation, neutralization and impurity removal temperature is 70-85℃ and the time is 0.5-1.0 h.

8. The method for producing cadmium cake from cadmium-containing dust according to claim 1, characterized in that, The acid solution in step (3) is one or both of dilute sulfuric acid and zinc electrolysis waste liquid.

9. The method for producing cadmium cake from cadmium-containing dust according to claim 1, characterized in that, Filter residue 1 and filter residue 2 are sent to lead smelting.

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